Hi ge7,
The steps in Message 4 explain how to do the levelled uninstall. A level-three and four uninstall is more comprehensive than the add-remove programs uninstall.
What printer do you have? In step 3 we need to download the software for your printer. We do not install this download, but we use the extracted files and perform the uninstall.
Use this link to find your product number How Do I Find My Model Number or Product Number?
Use this link to locate and download your software HP Drivers & Downloads.
With this, you can perform the steps in Message 4, the driver you downloaded with the link above replaces step 3 in message 4.
I hope this helps.